Secondary (also referred to as rechargeable) lithium metal batteries provide great promise for the next generation of energy storage devices due to the significantly higher energy density they provide. Unlike conventional lithium ion batteries, which contain anodes (also referred to as negative electrodes) formed from an intercalant material, such as graphite, lithium metal battery anodes are formed from lithium metal, for example, thin sheets of lithium metal coupled to current collectors. The intercalation anodes of lithium ion batteries only provide host structures for lithium ions and do not contribute to energy storage. Lithium metal battery anodes, by contrast, are formed, in part, by lithium metal, which contributes to energy storage, thereby significantly increasing volumetric and gravimetric energy density.
During charging and discharging cycles of a lithium metal battery, lithium metal is deposited onto the anode during charge and stripped from the anode during discharge. The morphology of the lithium on the surface of the anode varies throughout the life of the battery and is affected by a variety of variables. Spiky dendritic crystals of lithium metal, also referred to as dendrites, often form on the surface of a lithium metal anode. Also, a solid-electrolyte interphase (SEI) layer can form on the surface of the anode. As the number of charge-discharge cycles increases, an increasing amount of lithium can become “dead lithium” by becoming electrically isolated from the current collector of the anode, thereby making the isolated or dead lithium unavailable for further discharge of energy and reducing the coulombic efficiency of the cell. One form of dead lithium is dendritic crystals of lithium physically and/or electrically isolated from the electric conduction pathway to the current collection by in-situ formed SEI layers.